Controlled Oxygen Partial Pressure Research Articles

Effects of stomach inflation on haemodynamic and pulmonary function during spontaneous circulation in pigs

Aim Stomach inflation during mask ventilation is frequent, but the effects on haemodynamic and pulmonary function are unclear. We evaluated the effects of stomach inflation on haemodynamic and pulmonary function during spontaneous circulation in a porcine model. Methods Randomised prospective animal study. After randomisation, in 23 domestic pigs the stomach was inflated every 90 s with 0 L (control; n = 8), 0.5 L ( n = 7) or 1 L ( n = 8) ambient air. Results After 22.5 min, i.e. 8.5 L in the 0.5 L and 17 L in the 1 L stomach inflation group, stomach inflation increased central venous pressure (median) (control: 10 mmHg vs. 1 L: 23 mmHg, P < 0.05) and mean pulmonary artery pressure (control: 24 mmHg vs. 1 L: 45 mmHg, P < 0.05). As a result stroke volume index decreased (control: 135 mL/kg vs. 0.5 L: 90 mL/kg, P < 0.05; vs. 1 L: 72 mL/kg, P < 0.05). Stomach inflation also decreased static pulmonary compliance (control: 24 mL/cmH 2O vs. 0.5 L: 8 mL/cmH 2O, P < 0.05; vs. 1 L: 3 mL/cmH 2O, P < 0.05), which increased peak airway pressure (control: 28 cmH 2O vs. 0.5 L: 69 cmH 2O, P < 0.05; vs. 1 L: 73 cmH 2O, P < 0.05). Additionally, arterial oxygen partial pressure (control: 305 mmHg vs. 0.5 L: 140 mmHg, P < 0.05; vs. 1 L: 21 mmHg, P < 0.05) and systemic oxygen delivery (control: 53 mL O 2/min vs. 1 L: 19 mL O 2/min, P < 0.05) decreased. Stomach inflation increased mortality (control: 0/8 vs. 1 L: 5/8, P < 0.05). Conclusions Stomach inflation with 1 L when compared to 0.5 L increments resulted in faster haemodynamic and pulmonary failure and increased mortality. Stomach inflation may cause a hyper-acute abdominal compartment syndrome.

Degree of Undercooling and Contact Angle of Pure Iron at 1933 K on Single-crystal Al2O3, MgO, and MgAl2O4 under Argon Atmosphere with Controlled Oxygen Partial Pressure

Solid or molten oxides are considered to act as nucleation sites during continuous steel casting. The influence of the kind of oxide crystal and atmospheric oxygen partial pressure on the degree of undercooling and contact angle of pure molten iron on oxide substrates was measured by the sessile drop method. On Al2O3 and MgAl2O4 substrates, we found that the change in the degree of undercooling was dependent on the existence of a reaction layer and its thickness. On an MgO substrate, since no reaction layer formed, the degree of undercooling was small and was governed by the lattice misfit parameter. The equilibrium contact angle of a molten iron drop on the FeAl2O4 layer formed between the Al2O3 substrate and drop was about 100°; a similar contact angle was obtained on MgAl2O4. The contact angle on MgO changed during observation due to the evaporation of Mg.

Evaluation of dehydration mechanism during heating of hydrous asteroids based on mineralogical and chemical analysis of naturally and experimentally heated CM chondrites

Abstract Based on the evidence derived from spectroscopic observation and meteorite analysis, some hydrous asteroids were heated and dehydrated for a certain period of time after aqueous alteration. In order to reproduce the dehydration processes, we experimentally heated Murchison CM chondrite at 600°C for 1 h (600°C/1 h), 600°C/96 h, 900°C/1 h, and 900°C/96 h under controlled oxygen partial pressures. The experimental products were compared with Belgica (B-)7904 CM chondrite, a meteorite from a dehydrated asteroid in terms of characteristic mineralogical and compositional properties. B-7904 shows properties intermediate between the two experimental products heated at 900°C/1 h and 900°C/96 h. In addition, the presence or the absence of some temperature-sensitive minerals in B-7904 suggests that it experienced heating at a temperature higher than 700°C but lower than 890°C. The duration of heating, based on the diffusion time needed to achieve the Fe-Mg zoning profile in olivine in B-7904, was estimated to be between 10 and 103 days at 700°C and between 1 to 102 h at 890°C. The obtained durations are much shorter than those expected from the internal heating model which requires prolonged heating over million years. Therefore, it is unlikely that the short-lived radionuclide of 26Al is a heat source for the dehydration of B-7904. Instead, short-duration local heating, such as that from impacts or solar radiation, is a more promising heat source.

Microstructure and Interfaces of Thin Film Capacitors on Base Metal Foils

The microstructure and interface quality of chemical solution deposited barium titanate thin films on Ni foil were studied. Cross-sectional transmission electron microscopy shows that a ~200 nm thick barium titanate film annealed in a controlled oxygen partial pressure consists of equiaxed grains with grain size range of 24-75 nm (~ 42 nm average). NiO was detected after re-oxidation by X-ray diffraction, but not by transmission electron microscopy, suggesting that the oxide is not a continuous barrier layer, but is spatially distributed in the films. Oxygen non-stoichiometry and the existence of C in barium titanate films were observed by electron energy loss spectrometry. In addition, it was found that there is a 5-8 nm thick Ni-Ba alloy developed at the interface between the barium titanate film and Ni foil.

Phase Equilibria in Ferrous Calcium Silicate Slags: Part II. Evaluation of Experimental Data and Computer Thermodynamic Models

Ferrous calcium silicate slags (described by the FeO-Fe2O3-CaO-SiO2 system) are the basis for a number of slag systems used in nonferrous smelting. Characterization of this slag system is necessary to improve the design and optimization parameters of new processes, including fluxing and operating temperatures. Particularly of interest are the phase relations at intermediate oxygen partial pressures relevant to processes such as copper converting. Experimental data on the phase equilibria of these slags at controlled oxygen partial pressures in the temperature range between 1200 °C and 1350 °C are discussed, differences between various data sources are analyzed, and discrepancies are resolved. An evaluation of two thermodynamic computer models is undertaken to verify the computer-aided predictions using the experimental data. New experimental data for this system are reported for the temperature condition of 1300 °C, defined using the equilibration/rapid-quenching/electron probe microanalysis (EPMA) with wavelength dispersive detectors technique. This new information, combined with results from the previous study, has enabled the equilibrium liquidus compositions to be defined over a wide range of temperatures and oxygen partial pressures.

A multispectral imaging technique to determine concentration profiles of myoglobin derivatives during meat oxygenation

We have designed a multispectral imaging acquisition system to measure the relative concentration values of myoglobin forms inside meat during oxygenation. Images at 474, 525, 572 and 610 nm are used to compute the concentration of reduced myoglobin, oxymyoglobin and metmyoglobin with a spatial resolution of 0.0125 mm/pixel. From these images, pigment concentration profiles as a function of oxygenation time and depth beneath the surface were obtained. A model describing the diffusion of oxygen and the consumption of reduced myoglobin is numerically tested versus the measured concentration profiles. The model accurately fits the data with a Mean Root Squared Error equal to 0.253%. Precise definitions for position and width of pigment layers based in concentration profiles are given. The results suggest that multispectral imaging techniques combined with precise control and measurement of sample temperature and oxygen partial pressure will permit detailed studies of the myoglobin chemistry during oxygenation.

Effects of oxygen partial pressure control on the microstructure and PTCR properties of Ho doped BaTiO3

Effects of oxygen partial pressure ( \( {\hbox{P}}_{{\hbox{O}}_{\hbox{2}} } \)) control on the electrical properties and microstructural development of (Ba1-xHox)0.997TiO3 were studied. An oxidation condition (\( {\hbox{P}}_{{\hbox{O}}_{\hbox{2}} } \) ∼ 1.0 atm) was maintained during the heating process, and then the specimen was sintered in a reducing atmosphere (\( {\hbox{P}}_{{\hbox{O}}_{\hbox{2}} } \) < 10−9 atm) at 1350 °C, followed by the annealing process at 1000 °C and \( {\hbox{P}}_{{\hbox{O}}_{\hbox{2}} } \) = 1 atm. The switching temperature (TS) from the oxidation atmosphere to the reducing condition was changed from 1100 to 1350 °C. A significant decrease in the room-temperature resisitivity (ρ25) was observed as TS was increased. The temperature coefficient of resistance (TCR) was independent of the change in TS, and closed pores decreased with increasing TS.

Phase stability of MgO-doped Nd–Ba–Cu–O seed crystals for cold-seeded, OCMG processing

The thermodynamic stability of MgO-doped Nd1+xBa2−xCu3Oy (x=0–0.5) has been investigated as a function of solid solution level (x) under various oxygen partial pressures for use as a seed crystal composition in the melt growth of (LRE)-Ba–Cu–O (where LRE=light rare earth) bulk superconductors. The gradient of decomposition temperature, Tp, against solid solution level increases significantly with decreasing oxygen partial pressure, indicating that MgO-doped Nd–Ba–Cu–O (NdBCO) seed crystals should be grown under reduced pO2 to obtain seeds with high Tp. Based on these results, the optimum cold-seeded processing conditions for the fabrication of single grain GdBCO bulk superconductors containing silver (GdBCO/Ag) under a controlled oxygen partial pressure of 0.01atm have been determined. The onset Tc of GdBCO/Ag samples grown in air with the optimized seed crystal composition is improved significantly with increasing Ag content, indicating that silver addition to the precursor powder suppresses the formation of Gd–Ba solid solution.

Structural and electrochemical studies of annealed LiNiVO4 thin films

AbstractWe prepared stoichiometric lithium nickel vanadate amorphous thin films by using r.f. magnetron sputtering under controlled oxygen partial pressure. The amorphous films were heated at various temperatures, 300–600 °C, for 8 h. The as‐deposited and annealed thin films were characterized by Rutherford backscattering spectroscopy, nuclear reaction analysis, Auger electron spectroscopy, X‐ray diffraction, scanning electron microscopy and atomic force microscopy. The electrochemical behavior of the various films was studied by the galvanostatic method. The cells were tested in a liquid electrolyte at room temperature, with lithium metal used as the counter and reference electrode. The best electrochemical storage value was obtained with the thin film annealed at 300 °C, which showed superior capacity and small capacity loss during cycling. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Self-flux growth of single-crystalline Tl 2Ba 2CuO 6+ x

We report the growth of millimetre-sized single crystals of Tl 2Ba 2CuO 6+ x by a copper-rich self-flux technique. The crystals were annealed under controlled oxygen partial pressures and characterized. The interplay of oxygen non-stoichiometry, orthorhombicity, Cu substitution on the Tl site, and the superconducting properties is discussed.

Controlled Undercooling of Liquid Nickel in Contact with ZrO2 and Al2O3 Substrates under Varying Oxygen Partial Pressures

The objective of this study is to determine the conditions under which the inclusions present in liquid steel can act as heterogeneous nucleants for solidification. In order to study the factors that define the undercooling of a given metal/oxide couple, the undercooling of a pure iron sessile droplet in contact with Al2O3, ZrO2, and MgO substrates was measured under controlled oxygen partial pressures by observing droplet recalescence. The results showed that the undercooling of iron, in contact with a particular substrate, did not have a unique value, but was significantly affected by the oxygen content on the gas phase. For oxygen partial pressures between 10−21 and 10−19, the undercooling of iron on ZrO2 substrates was stable and around 290 °C. In the same range of oxygen partial pressure, the undercooling of iron on MgO substrates remained below 100 °C due to the low stability of this oxide. At lower oxygen contents, substrate decomposition might be the cause for the observed drop in the undercooling of iron on ZrO2 substrates to below 100 °C. The undercooling also decreased for increasing oxygen content as verified when the gas was changed from gettered Ar/Ar-H2 to CO/CO2 mixtures. The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deep undercooling observed in the ZrO2 experiments occurred when the highest contact angle between the liquid metal and the substrate was achieved.

Tl2Ba2CuO6+δ brings spectroscopic probes deep into the overdoped regime of the high-Tc cuprates

Single-particle spectroscopic probes, such as scanning tunnelling and angle-resolved photoemission spectroscopy (ARPES), have provided us with crucial insights into the complex electronic structure of the high-Tc cuprates, in particular for the under- and optimally-doped regimes where high-quality crystals suitable for surface-sensitive experiments are available. Conversely, the elementary excitations on the heavily overdoped side of the phase diagram remain largely unexplored. Important breakthroughs could come from the study of Tl2Ba2CuO6+δ (Tl2201), a structurally simple system whose doping level can be tuned from optimal to extreme overdoping by varying the oxygen content. Using a self-flux method and encapsulation, we have grown single crystals of Tl2201, which were then carefully annealed under controlled oxygen partial pressures. Their high quality and homogeneity are demonstrated by narrow rocking curves and superconducting transition widths. For higher dopings, the crystals are orthorhombic, a lattice distortion stabilized by O interstitials in the TlO layer. These crystals have enabled the first successful ARPES study of both normal and superconducting-state electronic structure in Tl2201, allowing a direct comparison with the Fermi surface from magnetoresistance and the gap from thermal conductivity experiments. This establishes Tl2201 as the first high-Tc cuprate for which a surface-sensitive single-particle spectroscopy and a comparable bulk transport technique have arrived at quantitative agreement on a major feature such as the normal state Fermi surface. The momentum dependence of the ARPES lineshape reveals, however, an unexpected phenomenology: in contrast to the case of under- and optimally-doped cuprates, quasiparticles are sharp near (π,0), the antinodal region where the gap is maximum, and broad at (π/2, π/2), the nodal region where the gap vanishes. This reversed quasiparticle anisotropy past optimal doping, and its relevance to scattering, many-body, and quantum-critical phenomena in the high-Tc cuprates, is discussed.

Dopingn-type carriers by La substitution for Ba in theYBa2Cu3Oysystem

Thus far, there is no cuprate system where both n-type and p-type charge carriers can be doped without changing the crystallographic structure. For studying the electron-hole symmetry in an identical structure, we try to dope n-type carriers to YBa2Cu3Oy system by reducing oxygen content and substituting La3+ ions for Ba2+. Single crystals of La-doped YBa2Cu3Oy are grown by a flux method with Y2O3 crucibles and it is confirmed that La actually substitutes \~13% of Ba. The oxygen content y can be varied between 6.21 and 6.95 by annealing the crystals in an atmosphere with controlled oxygen partial pressure. The in-plane resistivity rho_ab at room temperature was found to increase with decreasing oxygen content y down to 6.32, but interestingly further decrease in y results in a decrease in rho_ab. The most reduced samples with y = 6.21 show rho_ab of ~30 mOhm cm at room temperature, which is as much as seven orders-of-magnitude smaller than the maximum value at y = 6.32. Furthermore, both the Hall coefficient and the Seebeck coefficient of the y = 6.21 samples are found to be negative at room temperatures. The present results demonstrate that the non-doped Mott-insulating state has been crossed upon reducing y and n-type carriers are successfully doped in this material.

Oxygen nonstoichiometry, mixed valency and mixed conduction in (La,Sr)(Co,Fe)O 3− δ

Defect chemistry for a mixed conductor, La 0.6Sr 0.4Co 0.2Fe 0.8O 3− δ was studied. Samples were treated under controlled oxygen partial pressure, P(O 2), conditions at 1273 K [10 − 11.1 ≤ P(O 2)/atm ≤ 1], and cooled to room temperature. Oxygen nonstoichiometry and valences of transition metal ions for the treated samples were evaluated by iodometry and X-ray absorption spectroscopy, respectively. With decreasing P(O 2), preferential reduction of Co 3+ to Co 2+ was observed, while iron preserved its higher valence above 3 under conditions studied. A dependency of its electrical conductivity on P(O 2) was discussed along with a change in concentration of oxygen vacancies and mixed valences.

Oxidation behaviour of unirradiated sintered UO 2 pellets and powder at different oxygen partial pressures, above 350 °C

The oxidation of sintered UO 2 pellets and powder into U 3O 8 has been studied by thermogravimetry at 370 °C, under controlled oxygen partial pressures ( P O 2 ranging from 2 to 40 kPa). Sigmoidal curves of oxidation weight gain were measured for both pellet and powder test samples. The rate of oxidation increased as the oxygen partial pressure increased. It has been shown, by simultaneous TG-DSC, that the reaction proceeds in a pseudo steady state. An experimental methodology based on temperature or P O 2 jumps has shown that the assumption of a rate-limiting step is validated, and a mean value of activation energy for the formation of U 3O 8 of 103 kJ mol −1 was estimated.

High‐Temperature Oxidation of a Cu–Ni Based Cermet: Kinetic and Microstructural Study

The oxidation of a cermet composed of nickel ferrite (NixFe3−xO4), nickel oxide (NiyFe1−yO), and Ni–Cu alloy (CuzNi1−z) (with x=0.8, y=0.84, and z=0.44) has been studied by thermogravimetry, at 960°C, under controlled oxygen partial pressure. The rate of oxidation increases with the oxygen partial pressure up to 5.1 × 103 Pa, then it becomes independent of the oxygen pressure. This is due to the presence of the two copper oxides, CuO and Cu2O, above this oxygen pressure. Scanning electron microscopy observation of oxidized samples has shown that the oxidation mechanism involves both external and internal oxidation.

Experimental study on diamond dissolution in kimberlitic and lamproitic melts at 1300-1420 C and 1 GPa with controlled oxygen partial pressure

To evaluate the dissolution processes of diamond crystals in kimberlitic and lamproitic magmas, a series of diamond dissolution experiments were carried out in the graphite stability field at 1300–1420 °C and 1 GPa under the WI, MW, and HM buffers. Dissolution agents used include an aphanitic kimberlite from Wesselton Mine, South Africa, and a lamproite from Mount North, West Kimberley, Australia. With increasing run duration, diamond morphology changed from a sharp octahedron through combinations of octahedron and tetrahexahedroidal forms to spherical tetrahexahedroid having rounded faces. Negatively oriented trigons were formed on the octahedral {111} face. As the degree of diamond dissolution increased, the trigons changed from smaller shallow types to larger deep types. The dissolution rate in the kimberlitic solvent at 1300 °C was 0.12 mm/h under the HM buffer, 0.0034 mm/h under the MW buffer, and 0.0017 mm/h under the WI buffer, whereas that at 1420 °C was 0.014 mm/h under the WI buffer. In the lamproitic solvent, the dissolution rate was 0.0024 mm/h at 1420 °C under the WI buffer. The data indicate that diamond dissolves in silicate melts as carbonate ions through an oxidizing reaction. The degree of dissolution strongly depends on temperature, oxidation state, and the compositional dependence of CO 2 solubility in the melts.

Impact of Gaseous Additives on Copper CMP in Neutral and Alkaline Solutions Using a CAP System

A controlled atmosphere polishing (CAP) system was used to determine the effects of various chamber gases on copper chemical mechanical polishing (CMP) in the presence and absence of and . Using oxygen or nitrogen has only slight effects on copper removal rates in the presence of . Polishing without , performed with controlled oxygen partial pressure, demonstrates removal rates that are times higher than using nitrogen. Polishing using inert gases alone demonstrates an oxidant-starved system that reflects little dependence on wafer pressure or velocity. Addition of (pH 10) to experiments using oxidizing gases, such as oxygen and air, increases removal rates up to . Removal rates vary linearly with oxygen partial pressure using oxidizing gases for experiments using at pH 10. A trend indicating a transition from chemical to mechanical control is observed when concentration is increased at constant oxygen pressure. A copper removal mechanism in the presence of dissolved oxygen has been developed that highlights a buildup of oxidized copper at the wafer surface. The ability to perform CMP in a pressurized gaseous environment has shown that copper removal is a process of mechanical removal, dissolution of abraded material, and copper-oxygen reactions at the wafer surface.

Initial oxidation of Fe–Cr alloys: &lt;I&gt;in situ&lt;/I&gt; STM and &lt;I&gt;ex situ&lt;/I&gt; SEM observation

AbstractIn order to understand the initial oxidation of Fe–Cr alloys a single crystal of Fe–15Cr (100) was oxidized at 440°C under controlled oxygen partial pressure in a UHV system and the surface morphology was observed using in situ STM (basic pressure 1×10−10 mbar); in addition, polycrystalline Fe&15Cr was oxidized at 400°C in an IR-furnace in atmospheric air and the morphology was observed using ex situ SEM. The chemistry of the surface oxide layers was studied by XPS.Preparation of the single crystal in the UHV system did not lead to segregation of Cr to the surface during heating. In situ STM investigation showed that oxidation of Fe–Cr commenced by nucleation of Cr oxide on the surface, due to selective oxidation of Cr. When the Cr at the surface and at the interface was completely consumed by nucleation of Cr oxide, Fe oxidized and covered the initial Cr oxide nuclei, resulting in an Fe oxide layer on the surface. Ex situ experiments showed that initial oxidation of the mechanically prepared poly...

Control of Oxygen Partial Pressure by means of H2–H2O–O2 or CO–CO2–O2 Gas Mixtures

The electrical conductivity of as a function of was investigated in the two gaseous systems and . The experimental results showed different conductivity values for these two different systems. The oxygen partial pressure was, therefore, checked carefully and it turned out that the control of at reducing conditions is complicated by disequilibrium states when using gas mixtures. A sample and an oxygen sensor that are positioned side by side may be exposed to values that differ by up to 2 log units because of their different catalytic behavior with respect to the oxidation of CO. At intermediate conditions, e.g., between and at , low concentrations of (CO) and may result in gradients of up to 10 log units per centimeter in both and systems.